In general, an exhaust gas emitted from a vehicle engine contains unnecessary heat which is not useful, and is discarded in the outside air. However, exhaust may include a large amount of heat, and may account for about 30% of overall fuel consumption.
In a general gasoline or diesel engine, it is known that a quantity of heat of about 30% of the energy of fuel supplied to the engine is used for normal output consumption of the engine, about 30% thereof is a cooling loss, about 30% thereof is an exhaust loss, and about 10% thereof is consumed for driving other auxiliary devices. Since heat of about 30% is included in the exhaust gas is directly discharged and discarded in the air, heat loss can be reduced to enhance efficient operations. Thus, recently, a thermoelectric generator supplying electricity to a vehicle using an exhaust gas of the vehicle and an exhaust heat recovery device recovering heat of an exhaust gas to heat the interior of a vehicle have been used.
A thermoelectric element may refer to an element using a thermoelectric effect for converting a temperature difference between both ends of a device into electricity to thus convert thermal energy into electric energy or allowing electricity to flow in a device to cause a temperature difference between both ends of the device to convert electric energy into thermal energy.
However, if exhaust heat is indiscriminately recovered, a harmful emission emitted from an engine may not be appropriately purified in a catalytic converter. That is, a catalyst cannot smoothly exhibit a purification function until the catalytic converter arrives at a light-off temperature (LOT), increasing an amount of harmful emissions in the exhaust gas. Thus, a system for reducing harmful emissions while also recovering exhaust heat is desirable.